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VulnerabilityPublished Updated

CVE-2026-72043: Linux kernel · LoongArch: Fix missing dirty page tracking in {pte,pmd}_wrprotect()

Affects Linux kernelSource GCVE Database

0

Not known to be exploited · CVSS 7.1 High.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score
7.1High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 17 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

AI-suggested

A fix has been implemented in the Linux kernel source to propagate the _PAGE_DIRTY bit to the _PAGE_MODIFIED bit in pte_wrprotect() and pmd_wrprotect() functions. Users should apply the official Linux kernel updates that include this fix. Since this is a kernel-level issue, upgrading to a patched kernel version is the recommended remediation. Patch status is not explicitly stated in the input data; check the Linux kernel vendor advisory or source repository for the exact fixed version and apply updates accordingly.

Description

In the Linux kernel, the following vulnerability has been resolved: LoongArch: Fix missing dirty page tracking in {pte,pmd}_wrprotect() When hardware page table walker (PTW) is enabled on LoongArch, the CPU may set _PAGE_DIRTY directly in the page table entry during a write TLB miss, without going through the software TLB store handler. The software TLB store handler (tlbex.S:254) sets both _PAGE_DIRTY and_PAGE_MODIFIED together: ori t0, t0, (_PAGE_VALID | _PAGE_DIRTY | _PAGE_MODIFIED) Since hardware PTW only sets _PAGE_DIRTY, the software-only bit, i.e. _PAGE_MODIFIED is left unchanged. This creates a window where a PTE has _PAGE_DIRTY set (hardware knows the page is dirty) but _PAGE_MODIFIED clear (software is unaware). When fork()/clone() triggers copy-on-write, __copy_present_ptes() calls pte_wrprotect(), which unconditionally clears both the _PAGE_WRITE and _PAGE_DIRTY bits: pte_val(pte) &= ~(_PAGE_WRITE | _PAGE_DIRTY); Since _PAGE_MODIFIED was never set, the dirtiness information is lost completely. Subsequently, when memory pressure triggers page reclaim, page_mkclean() / try_to_unmap() sees the page as clean (i.e. pte_dirty() returns false) and the page may be freed without writeback, causing data corruption. Fix this by propagating the _PAGE_DIRTY bit to the _PAGE_MODIFIED bit in both pte_wrprotect() and pmd_wrprotect() before clearing writeable bits: if (pte_val(pte) & _PAGE_DIRTY) pte_val(pte) |= _PAGE_MODIFIED; The pmd_wrprotect() fix handles the CONFIG_TRANSPARENT_HUGEPAGE case, where pmd entries need the same treatment. This ensures the software dirty tracking bit (checked by pte_dirty() and pmd_dirty(), which read both the _PAGE_DIRTY and _PAGE_MODIFIED bits) is preserved across fork COW write-protection. The issue was found by the LTP madvise09 test case, which exercises page reclaim after "madvise(MADV_FREE), write and fork" operation sequence on private anonymous mappings.

References

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